Recently, in the light of resources saving, energy saving and in addition, protection of environment, a strong demand for reduction of exhausted carbon dioxide is increasing, and various countermeasures such as weight saving of a vehicle and use of electric energy have been considered. Accordingly, it is demanded to enhance fuel efficiency by decreasing rolling resistance of a tire for a vehicle, and also improvement of performances such as durability is desired.
For example, there are known, as a method for decreasing rolling resistance, techniques such as blending of silica, decrease in an amount of a filler, use of a filler having less reinforcing property. However, there is a tendency that a mechanical strength of a rubber decreases and various performances are degraded.
In JP 2009-120819 A, use of a silane coupling agent having a highly reactive mercapto group (mercapto silane coupling agent) for the purpose of improving performance such as fuel efficiency has been considered. However, in a mercapto silane coupling agent, good fuel efficiency, wet grip performance and abrasion resistance are obtained while since the mercapto silane coupling agent has high reactivity, there is a concern that gelation occurs during kneading with a rubber component and processability is lowered.
Meanwhile, JP 2012-046602 A describes that in a rubber composition for a base tread which enables fuel efficiency, elongation at break and durability to be improved in good balance while good steering stability and processability (extrusion processability) are maintained even if an amount of zinc oxide is decreased, crosslinking of polymers can be made uniformly by blending a specific zinc dithiophosphate.